Hi roottalk,
I'm having trouble looping over entries in array variables using
TTree::Draw under a specific circumstance.
I've placed an example in:
http://www.hep.umn.edu/~schubert/roottest/ntptest.tar.gz
The example consists of three simple classes:
class NtpShower : public TObject {
...
Float_t fEnergy; // shower energy
ClassDef(NtpShower,1) //A reconstructed shower
};
class NtpEvent: public TObject {
...
Int_t fEventNo; // event number
Int_t fNShower; // number of showers in this event
Int_t* fShwInd; //[fNShower] array of indices into shower TClonesArray
ClassDef(NtpEvent,1) //A reconstructed event
};
class NtpRecord:public TObject {
...
TClonesArray* fShowers; //~> Array of showers
TClonesArray* fEvents; //-> Array of events
ClassDef(NtpRecord,1) //A reconstructed spill record
};
These classes are set up so that the user can use the shower indices stored
in the NtpEvent class to map back to the NtpShower objects stored in the
fShowers
TClonesArray.
In the test program FillNtp, a tree is created with a single main branch
to hold NtpRecord objects,
split at level = 99, One NtpRecord is generated and the fShowers array
is filled with 3 NtpShowers:
// shower 0 has fEnergy 10
// shower 1 has fEnergy 20
// shower 2 has fEnergy 30
and 4 NtpEvents:
// event 0 has 2 showers with fShwInd values of 0 &1
// event 1 has 0 showers
// event 2 has 1 shower with fShwInd value of 2
// event 3 has 0 showers
Now I try to use the arrays in a Draw (or Scan loop) and I find that the
results aren't what I expect.
For example,
tree ->
Scan("fShowers[fEvents[].fShwInd[0]].fEnergy","fEvents[].fNShower > 0");
yields:
***********************************
* Row * Instance * fShowers[ *
***********************************
* 0 * 0 * 10 *
***********************************
==> 1 selected entry
instead of the expected 2 entries. I can get 2 entries if I leave off
the selection string, but I find
I need this selection string to avoid array out of bounds if the first
argument to Scan or Draw
becomes more complicated, e.g.:
tree -> Scan("fEvents[].fNShower:fShowers[fEvents[].fShwInd[0]].fEnergy");
causes a rather enormous list of array indexing errors.
Is this a bug or is there an error in the way I'm expressing the loop
over the arrays?
Thanks,
-Sue
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